The next build of SyntaxEditor for WPF will have a number of new properties added to the SyntaxEditor control that let you configure the caret and selection brushes used in the control:
- CaretBrush
- SelectionBackgroundActive
- SelectionBorderActiveBrush
- SelectionBackgroundInactive
- SelectionBorderInactiveBrush

We’ve also built a new QuickStart showing how easy it is to change colors and give your editor a truly unique look.
These sort of features will also be available in the upcoming Microsoft .NET 4.0 release for common controls such as TextBox too. See this post for caret brush details and this post for selection brush details.
With these new features in SyntaxEditor, you’ll be able to ensure your SyntaxEditor caret and selection brushes match those of the other native WPF controls, even when you create custom themes.